The piquancy, pungency, “spicy heat,” or “spicy hotness” of various substances depends upon particular chemical compounds carried by the substances. The sensation of piquancy, pungency, “spicy heat,” or “spicy hotness” is a chemesthetic phenomenon involving somatosensory nerve pathways (e.g., nociceptive pathways), and is distinct from other types of taste phenomena. For purpose of simplicity and to aid understanding, piquancy, pungency, or “spicy hotness” is referred to hereafter as spiciness.
Commonly, the sensation of spiciness results from tissue exposure to compounds known as capsaicinoids. The capsaiciniods are amides formed from condensation of vanillylamine and fatty acids of different chain lengths. The particular forms of different natural capsaicinoids depend on the number of lateral chain carbon(R) and/or the presence, absence, or extent of (un)saturation. Capsaicinoids are synthesized naturally, for instance, in the placenta of chili fruits from enzymatic condensation of vanillamine and different-sized fatty acid chains, which are elongated by a fatty acid synthase. The capsaicinoind family includes capsaicin, dihydrocapsaicin, and other compounds shown below.

A conventional measurement of spiciness is the Schoville Heat Unit (SHU), which is measured by way of the Schoville organoleptic technique or test (See W.Scoville, J Am Pharm. Assoc., 1, 453, (1912)). According to this technique, a pepper extract is diluted in sugar syrup until the heat or pungency is no longer detectable to the tongues of a panel of five tasters (specially trained volunteers). However, the greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity. An alternative technique for quantitative measurement of spiciness is high pressure liquid chromatography (HPLC), which measures spiciness in terms of ASTA pungency units. While HPLC is more objective and accurate than the traditional Scoville Unit, it is also much more complex and costly.
Some researches have additionally studied electrochemical techniques for detecting capsaicinoids. Electrochemical techniques involve determining relationships between electrical potential and the concentration of redox species at an electrode surface. For detecting capsaicinoids, electrode surfaces have been modified by way of nano-scale structures such as Multi-walled Carbon nanotubes (MWCNTs). However, such electrode surface modification results in unnecessary expense and complexity, and can limit electrode performance or measurement reliability in certain situations. Therefore, there is a need for more cost efficient and/or simpler techniques for detecting spiciness in a sample.